Best for mostFolger Shakespeare Library · 1993
For almost everyone, the Folger is the right Othello. Notes face the text, so you keep your footing through Iago's fast, insinuating speech without diving to the bottom of the page. Cheap, clear, and the classroom standard. This is where I'd start.
Most scholarlyArden (3rd series) · 1997
The Arden Third Series, edited by E. A. J. Honigmann, is the scholar's Othello — a major introduction and dense footnotes, including on the play's two early texts (Quarto and Folio) and on its long, fraught history on stage. Indispensable for study; more than a first read needs.
Best one-volume scholarlyOxford Shakespeare · 2006
Michael Neill's Oxford edition is widely admired — serious scholarship in one volume, with an unusually thoughtful introduction on the play's treatment of race and jealousy. The step up from Folger if you want depth without the full Arden.
For beginnersNo Fear Shakespeare · 2003
No Fear sets the original beside a plain modern paraphrase. You lose the poetry — and Othello's is some of Shakespeare's most charged — so treat the modern side as a helper, not the real thing. But if the language has defeated you before, it can carry you through.
William ShakespeareOthellotr. Free (public domain)
FreeFree (public domain) · 1622
Othello is public domain, so the full text is free — Folger Digital Texts, MIT, Project Gutenberg. No glosses for the harder lines, but it's the whole play at no cost, good for sampling or re-reading a scene.